Clear pk context and other minor changes in *_free() procedures
diff --git a/library/pem.c b/library/pem.c
index 6069a23..897c8a0 100644
--- a/library/pem.c
+++ b/library/pem.c
@@ -423,9 +423,11 @@
 
 void mbedtls_pem_free( mbedtls_pem_context *ctx )
 {
-    if( ctx->buf != NULL )
+    if ( ctx->buf != NULL )
+    {
         mbedtls_platform_zeroize( ctx->buf, ctx->buflen );
-    mbedtls_free( ctx->buf );
+        mbedtls_free( ctx->buf );
+    }
     mbedtls_free( ctx->info );
 
     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_pem_context ) );